Cutting tools, manual scissors or shears type, are used for progressive cutting of a material. Hand shears work with a cross lever, and necessarily require human power to hold and operate them; they are used in different fields of human activity, including gardening and growing and harvesting of flowers and fruits. These mechanisms are known as bypass cutting and usually consist of a sharp steel blade at 23° and a counter-blade, also in steel, called anvil which provides support to the stem while being sheared. This system produces a net cut bezel that is used for any kind of pruning, from formation to maintenance and fructification.
However, existing tools in the prior art are not the most appropriate for the tasks in intensive crops such as flowers or fruit, because they cause muscle tension, awkward postures, contact pressure and other health risks for workers, which can lead to damage such as lesions in the hand, wrist and arm (such as tendinitis or carpal tunnel syndrome—CTS), engaging in turn muscles, nerves, tendons, ligaments, joints, cartilage and blood vessels in the upper extremities. To this is added a repetition of moves that leads to small muscle fatigue, an impact that worsens with mandatory use of gloves, demanding the worker an additional effort, which increases the danger of injury.
Most flower farms in Latin America use imported scissors (Felco® and Bahco®), which were designed for people of different anthropometric measures and were not specifically designed for cutting flower stems. These circumstances generate an extra effort when the worker hold them and operate them.
Added to this, the position adopted by the hand-wrist joint, produces radial and ulnar deviations, which with the passage of time and the repeatability demanded by the activity, are detrimental to the limb.
In an attempt to avoid or reduce these negative effects, in recent years there have been numerous designs in the area of hand tools to meet the needs of the end user. Among them is the invention disclosed in patent EP0529566, which presents gardener shears provided with an upper handle with a counter blade, a lower handle equipped with a blade and a scissors joint, which presents two sections articulated in form of superposed annular discs. These sections are attached to the blade and to the counter blade. They also have a threaded sleeve with a threaded joint screw, means for absorbing the radial load and independent means for absorbing the axial load. These shears are characterized by having in its upper part outside the cutting zone of the blade and counter blade, on the periphery of the articulated sections in form of annular discs of the upper handle and lower handle, respective notches or cracks that can be matched and that function as wire cutters.
The document EP 0704150 presents cutting pliers for one hand, comprising in particular a first handle having a cutting blade and a second handle having a counter blade or a second cutting blade, the two handles being connected by a pin in order to permit cutting with scissors effect, wherein one of the two handles is longer than the other handle, the extra length of the longer handle being such that the user can easily press with the palm of the second hand on the length available beyond that already used by the fingers of the first hand. The cutting shears also comprise a compression spring located between the first and second handles, means for regulating a force of pivoting friction at the pin connecting the first and second handles, means for locking the nippers in a closed position, means for limiting movement in a closing direction, means for limiting movement in an opening direction and means for protecting the first and second handles.
The application GB996685 relates to shears and similar tools comprising a handle, which is used as a support for the first, second, third and fourth fingers, and the grip stock of which is movable relatively to the associated handle arm whereas the grip stock against which the thumb bears is connected fast to the associated handle arm. So, the movable grip stock is adapted to rotate about the longitudinal axis of the associated handle arm and that the longitudinal axis of the movable grip stock is disposed obliquely to the longitudinal axis of the associated handle arm in such a manner that the two longitudinal axes form an acute angle with one another, the apex of which is in the vicinity of the first finger bearing zone, the longitudinal axis of the movable grip stock being situated, in the vicinity of the outer end thereof, when the shears are closed, nearer to the fixed grip stock than the longitudinal axis of the associated handle arm, so that all the phalanxes of the first, second, third and fourth fingers when the shears are opened and closed bear at least approximately with their full internal surfaces against the movable grip stock.
The American document U.S. Pat. No. 5,469,625 presents a hand pruner which provides a maximum force on the blades when the handles are closed halfway with a constant force being applied to the handles. It has an ergonomic configuration of the operating handle which is bent at the operating end to permit better viewing of the cutting blades as well as reducing carpal tunnel fatigue in the arm of the operator. The hand pruner presented in this document comprises a first handle having a first pivot section and a handle section (the handle pivots to an angle of maximum 30° with respect to the second handle). A second handle having a second pivot section
and a second handle section, a first pin pivotally connecting said first pivot section to said second pivot section, a hook having one end pivotally connected to said second handle section, a bolt pivotally connecting said one end of said hook to said second handle section, a stationary cutting blade mounted in said second handle section and having one end secured to said bolt and the other end located in the path of travel of said hook and a pair of links connecting said hook to said first pivot section whereby the pivotal movement of said first handle with respect to said second handle will pull the hook into engagement with said stationary blade. In one embodiment the invention includes an anvil mounted on the hook into the path of travel of the blade.
The American application US2005252353 shows a grip comprising an angled handle, at least one fixing element, and a tool fastening portion arranged at the end portion of the angled handle. The fixing element may be connected with a bottom part of the angled handle in such a manner that the distance between the angled handle and the fixing element is adjustable to allow an object to be firmly engaged so that it may be securely avoided that the tool is undesirably lost (for instance falls down).
The handle and the fixing element may be made of a deformable material and may be firmly connected to each other. An elongated hole is formed in the angled handle; a pin corresponding to the elongated hole is provided and attached to the fixing element. The pin extends through the elongated hole to allow guiding the fixing element with respect to the angled handle by shifting the pin along the elongated hole. The shear may comprise an operating lever with a stripping-off edge, a fixed pivotal point and a retracting element, for instance a spring element. The user may fasten four of her or his fingers and operate the operating layer with his or her thumb to perform the cutting quickly and accurately. The retracting element may drive back the cutting elements into their biased initial position. In an alternative embodiment of this invention, the handle may include a knob to adjust the distance between the angled handle and the fixing element.
Finally, the Spanish application ES279948 presents a hand tool for cutting and harvesting leathery stemmed agricultural products, particularly fruits such as grapes. It comprises a handle formed by two articulated arms around a pivot axis. The arms are bent and have at their ends a pick carrying the cutting elements. The pick axis forms an angle between 60° and 150° with the axis of the handle. The elements are composed of a removable blade attached to the pick by two pins and by a flange that serves to support the cutting blade. The pick has an angled profile and the flange has a flat surface, relatively wide, which is opposed to the inner surface of the pick carrying the cutting blade, forming a clamp arranged to grab the stem of the fruit after cutting. One feature of the tool is that one of the arms of the handle is provided with a spring to bear against the other arm, to maintain the two picks in the open position and where at least the clamping surface of the lower pick is serrated. This tool ensures that, regardless of the diameter of the stem of the fruit to be cut, and with the condition that this is introduced into the bottom of the opening of the tool, the gripping surfaces of the two picks come into function to grip the stem and retaining the fruit before the blade cuts the stem completely. Additionally, with limited opening angle of the picks, the operator doesn't have to make any effort to limit the separation of the arms of the handle, since it only has to overcome the resistance of the spring during the cutting phase, thereby reducing fatigue.
Despite the existence of various hand tools on the market, it is necessary to design a tool for cut flowers or fruits with a smoother recoil spring and a smaller opening of the handles of the scissors. Likewise, we should take into account parameters such as tool weight, anatomical handles designed according to workers anthropometry in fruit crops and floriculture in Latin America, optimization of the length of the blades, the angle between the handles and the level of the blades, and improvement of the gravity center position of the tool relative to the hand.
Other characteristics which should be taken into account are the structure of the gripping surface and its materials, including degree of friction, the possibility of using different handles, the mechanical strength required for its operation, the transmission level of the forces and the use of gloves as their use increases the force required for said operation.